THE NUCLEUS IN HEREDITY 33 



somes remain distinct, the paternal from the maternal, for 

 at least several generations of cells. 1 



We must also remember that while an accurate division 

 of the nuclear contents takes place, the cytoplasm seems to 

 divide in bulk without anything very marked in the way 

 of selective division. 



There are many biologists who accept the theory that 

 the chromatin is the substance in the cell that conveys the 

 hereditary character from generation to generation of cells. 

 The waxing and waning of the chromatin, and its occasional 

 disappearance, 2 seems to suggest, as has already been stated, 

 that linin should be taken rather than chromatin, if a par- 

 ticular part of the nucleus is really the vehicle of hereditary 

 characters, but this is perhaps a minor point, and we will 

 take the theory in the sense of dealing with the chromosomes 

 and that part of the nucleus which goes to form them. 

 Granting this, it seems eminently probable that such a 

 substance is handed on from cell generation to cell generation 

 in a selective manner. 



The wide consideration given to this theory may be 

 adequately estimated by the following quotation : Professor 

 E. B. Wilson, referring to the observations just cited, says: 

 " It was in the main these considerations that led Hertwig, 

 Strasburger, Kolliker, and Weismann, independently and 

 almost simultaneously, to the conclusion that the nucleus 

 contains the physical basis of inheritance, and that 

 chromatin, its essential constituent, is the idioplasm postu- 

 lated in Nageli's theory. This conclusion is now widely 

 accepted and rests upon a basis so firm that it must be 

 regarded as a working hypothesis of high value." 3 We 



1 Riickert, J., " Uber das Selbstandigbleiben der vateiiichen und nmtter- 

 lichen Kcrnsubstanz wahrend der ersten Entwicklung des befruchteten Cyclops- 

 Eies," Arcldv fur mikroscopische Anatomic, xlv. 3, 1895; Herla, V., "Etude 

 des Variations de la mitose chez 1'ascaride me'galoce'phale, " Archives de Biologic, 

 xiii., 1893 ; Zoja, R., "Sulla independenza della chromatina paterna e materna 

 nel nucleo delle cellule embrionali, Anatomischcr Anzeiger, xi. 10, 1905. 



2 See p. 19. 



3 The Cell in Development and Inheritance, p. 403, 1904. 



C 



